Optical parametric oscillators (OPO) are known in the prior art. See: U.S. Pat. Nos. 6,108,356 and 5,841,798. Prior art OPO devices can have limited useful lifetimes due to coating failure on the OPO crystal. In addition, prior art OPO devices often have power limitations. The damage threshold of the crystal and crystal coatings limits the amount of power that can be produced. On the other hand, the laser threshold of the OPO crystal limits low power applications. As a result, there is a need in the art for improved optical parametric oscillators particularly lasers that can produce eyesafe wavelength beams.
The subject invention also relates to lasers where the final output wavelength is 193 nm. In many fields such as lithography (metrology of 193 nm stepper lenses), calibration of precision DUV spectrometers, mask inspection, there is a need for low powered 193 nm lasers. Generally complex Ti:sapphire lasers have been used to provide low power lasers having a wavelength of 193 nm for these applications. Typically such lasers are complicated and require two lasing crystals lasing at different wavelengths. See for example U.S. Pat. Nos. 6,088,379 and 6,240,111. Thus there is a need for simple lasers that can provide 193 nm beams.